γ-Ray Spectroscopy at the Limits: First Observation of Rotational Bands inLr255

Abstract

The rotational band structure of 255Lr has been investigated using advanced in-beam gamma-ray spectroscopic techniques. To date, 255Lr is the heaviest nucleus to be studied in this manner. One rotational band has been unambiguously observed and strong evidence for a second rotational structure was found. The structures are tentatively assigned to be based on the 1/2-[521] and 7/2-[514] Nilsson states, consistent with assignments from recently obtained alpha decay data. The experimental rotational band dynamic moment of inertia is used to test self-consistent mean-field calculations using the Skyrme SLy4 interaction and a density-dependent pairing force.

Properties of nuclei in the nobelium region studied within the covariant, Skyrme, and Gogny energy density functionals

“…[45]. With that, the proton pairing strength is significantly larger than that given by the standard value of V n = V p = −1250 MeV fm 3 used for heavy nuclei in previous publications [39,7,[40][41][42][43] (which all have been carried out using the Lipkin-Nogami (LN) scheme, though). These previous values were obtained by adjusting moments of inertia in rotational bands of heavy nuclei [45].…”

“…For the coupling constants of the so-called time-odd terms that contribute to cranked and blocked states, the same "hybrid" choice was made as in many earlier calculations [7,[31][32][33][38][39][40][41][42][43][44]. They were set to the "native" values dictated by a density-dependent Skyrme two-body force for all terms except for those that multiply terms that couple two derivatives and two Pauli spin matrices.…”

One-quasiparticle states in odd-Zheavy nuclei

“…While in Refs. [3,26] the 1/2 − [521] level was assigned to the ground state, in Ref. [7] the lowest rotational band was found to be built on the 9/2 + [624] state.…”

High-K multi-particle bands and pairing reduction in 254No *

“…The spin-orbit interaction strength of 2f 5/2 − 2f 7/2 partner controls whether the proton Z = 114 is a magic number for the "island of stability" for shell stabilized superheavy nuclei. Rotational bands based on π 1 2 − [521] orbital have been observed in odd-proton nuclei 251 Md [13] and 255 Lr [14]. Studies of these rotational bands found a significant signature splitting [15,16].…”

“…The spin-orbit interaction strength of 2f 5/2 − 2f 7/2 partner governs the size of the Z = 114 spherical shell gap, which is predicted as the possible next magic proton number beyond lead. The properties of single-particle orbitals π 7 2 − [514] and π 1 2 − [521] effect strongly the properties of the neighboring odd-Z nuclei [13][14][15][16].…”